Apparatus for actuating a limit control element

ABSTRACT

A device for actuating a control element such as a limit switch. The device has an actuating arm which is rotated to actuate the switch. The arm is adjustable, without disassembling the device, to provide three modes of switch operation; one in which the switch is operated only by clockwise rotation of the arm, a second in which only counterclockwise arm rotation produces switch operation, and a third in which the switch is operated by rotation in either direction.

United States Patent Ustin 1 Sept. 5, 1972 [54] APPARATUS FOR ACTUATINGA 3,045,503 7/1962 Kiessling ..200/166 N X LIMIT CONTROL ELEMENT3,303,298 2/ 1967 Dobes ..200/47 [72] Inventor, Martin Usfin Pine Brook,NJ 3,546,954 12/1970 Ustm ..200/47 x [73] Assignee: Buchanan ElectricalProducts Cor- F N T NT R APPLICATIONS 1,100,670 4/1955 France ..74/568[22] Filed: Sept. 29, 1970 1,004,031 9/1965 Great Britain ..74/568 [21]Appl' 76568 Primary Examiner'-Robert K. Schaefer Related US. ApplicationData Assistant Examiner-William J. Smith [62] Division Of Ser. NO.567,172, July 22, 1966, Saffmd Pat. No. 3,546,954. [5 ABSTRACT Cl 7 R Adevice for actuating a control element such as a [51] Illlt. Cl witchThe has an actuating arm which is F'eld of Search-w, 153-13, 166 N,rotated to actuate the switch. The arm is adjustable, 200/24 29? 74/10714691 568 R without disassembling the device, to provide three modes ofswitch operation; one in which the switch is [56] References cuedoperated only by clockwise rotation of the arm, a UNITED STATES PATENTSsecond in which only counterclockwise arm rotation produces switchoperation, and a third in which the 3,252,345 5/1966 Russell ..200/47 XSwitch is operated by rotation in either direction 3,120,595 2/1964 Corket a1 ..200/153 CB 2,474,945 7/1949 Johnson ..200/47 X 7 Claims, 7Drawing 2a H J? /00 My 04 /G 2? "80 z; if

4f? j i P'A TENTEDsEP 51912 I 3.688.593

SHEU 2 [IF 2 INVENTOR.

MAkT/A .9 05 7/ APPARATUS FOR ACTUATING A LIMIT CONTROL ELEMENT Thispatent application is a division of US. application Ser. No. 567,172,filed July 22, 1966 now US. Pat. No. 3546954, issued Dec. 15, 1970.

This invention relates to electrical switching devices;more-particularly, this invention relates to electrical limit switchesand means for mechanically actuating such limit switches.

A limit switch typically is used to stop a mechanical movement byturning off the energization to a motor causing the movement when themovement has proceeded as far as is desired. For example, the switchoften is positioned near a machine to limit the movement of a cuttingtool. The limit switch usually has an actuating arm or plunger with aroller on it. When a machine component contacts the roller and depressesthe plunger or rotates the arm, this mechanical movement opens or closesan electrical switch so as to stop the movement of the machinecomponent.

One problem with such prior limit switches is that the orientation ofthe actuating arm or plunger cannot easily be changed so as to properlyengage machine components moving at various different angles. As aresult, often it is necessary for the user of such switches to maintaina variety of different mounting brackets for mounting the switches, eachbracket providing a different fixed angle for the actuating member.Furthermore, considerable labor is required in changing the brackets.Additionally, the provision of a variety of brackets does not provideinfinite variability of position of the actuating arm. If a particularangular orientation is desired and a standard bracket is not suitable, aspecial bracket must be made at great cost.

One partial solution for the above problem which has been proposed is tomake the switch mechanism in two parts, a switch housing and a headportion mounted on top of the housing with the actuating arm attached tothe head portion. By loosening several mounting screws, turning the headwith respect to the housing, and again tightening the mounting screws,the actuating member can be positioned in any one of four angularpositions spaced 90 from one another. However, the provision of thesefour positions does not solve the problem because many other angularpositions often are desired. Furthermore, the adjustment of the headposition is time-consuming and costly. Also, multiple types of bracketsoften still must be maintained by the user in order to providesufficient variability of the adjustment angle.

Accordingly, one object of the present invention is to provide aswitching device with a switch actuating member infinitely positionableangularly with respect to the mounting structure of the device. It isanother object of the present invention to provide such a device whichis quickly and easily positionable with great accuracy, and which can beadjusted without disassembling the switch. It is a further object of theinvention to provide such a device which is relatively simple toconstruct, reliable in operation, and inexpensive to manufacture.

Another problem is met in using the type of limit switch having arotatable arm for an actuating member. This problem is that often it isdesired to change the direction in which the arm is to be rotated inorder to operate the switch. That is, in some uses it is desired to havethe arm operate the switch only when the arm is rotated in a clockwisedirection. In other instances, it is desired to have the am operate theswitch only when the arm is rotated in a counterclockwise direction. Instill other uses of the switch, it is desired to have the arm operatethe switch both when it is rotated clockwise and when it is rotatedcounterclockwise.

Prior art limit switches have provided a certain amount of variabilityof the actuation direction. However, the amount of effort required tochange the actuation direction has been considerable, and it is believedthat all three of the above-described modes of operation have not beenprovided in any one practical device.

Accordingly, it is another object of the present invention to provideswitching device with a rotatable actuating arm, the device beingcapable of being adjusted easily and simply to vary the direction ofswitch actuation, and can be adjusted to provide all three of theabove-described modes of operation. It is another object of the presentinvention to provide such a device whose actuating arm is infinitelypositionable angularlywith respect to the support member of the device,and to provide a simple, reliable and versatile limit switch.

Other object and advantages of the present invention will be pointed outin or apparent from the following description and drawings.

In the drawings:

FIG. 1 is a front elevation view of a preferred embodiment of theinvention;

FIG. 2 is a partially broken-away cross-sectional view taken along line2-2 of FIG. 1;

FIG. 3 is a perspective view of several of the components of thestructure shown in FIGS. 1 and 2;

FIG. 4 is an enlarged, partially broken-away view of a portion of thestructure shown in FIGS. 1 through 3;

FIG. 5 is a cross-sectional view taken along line S-S of FIG. 4;

FIG. 6 is a cross-sectional view taken along line 66 of FIG. 4; and

FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 2.

FIGS. 1 and 2 show a limit switch 10 including a switch housing 12, acam housing or head 14 rotatably mounted on the switch housing 12, a camshaft 16 rotatably mounted in the head 14, and an actuating arm 18secured to the shaft 16. The actuating arm 18 has a roller 20 mounted atits outermost end. Two cams 22 and 24 are mounted on shaft 16 and engagea cam follower rod 26. Cam follower rod 26 engages a spring-biasedswitch switch button 28 of a conventional snap-acting switch 30 which ismounted in the switch housing 12.

Briefly, the switch 10 operates as follows: The physical object whosemotion is to be limited moves into contact with the roller 20 androtates the arm 18 and shaft 16 either clockwise or counterclockwisefrom a neutral starting position. The rotation of shaft 16 rotates cams22 and 24, thus causing the cam follower rod 26 to be pushed downwardlyagainst the switch button 28 of switch 30. The depression of button 28causes the contacts of the switch 30 to snap open or shut. When thephysical object moves away from the roller 20, the arm 18 returns to itsneutral position under the influence of a spring return mechanism, to bedescribed below, and the switch button 28 is returned to its uppermostposition in which the contacts of the switch are once again in theirinitial condition.

In accordance with the present invention, the arm housing or head 114 isrotatably mounted on the switch housing 12. Head 14 is substantiallycylindrical in shape and has screw threads 32 cut into its lower edge.As is shown in FIG. 2, a worn gear 34 is rotatably mounted on a pair oftabs 36 and 38 extending upwardly from a recessed portion of the housing12. The worm member 34 is held in position by means of a pair ofsnap-rings 40 and 42 which are fitted into grooves in the shaft portionof the worm member 34 near the tabs 36 and 38. The worm gear 34 mesheswith the teeth 32 cut in the lower edge of the head 14. Its shaft hasslotted ends (see FIG. 2) so that the worm can be turned by means of ascrew driver. Thus, the angular position of the head 14 with respect tothe housing 12 can be varied infinitely through a full circle merely byturning the worm 34 with a screw driver. The worm gear firmly locks thehead 14 so that it will not turn after is have been set to a desiredposition.

A cover 44 (shown only in FIG. 2) is positioned around the worm 34 andthe threads 32 in order to protect them from dust and dirt. The cover 44is marked with degree markings (not shown) so as to indicate therelative position of the head 14 with respect to the switch housing 12.In accordance with the present invention, the slotted ends of the wormshaft are exposed so that the position of the actuating arm 18 can beadjusted from the outside without entering either housing 12 or 14.

The housing 12 has a pair of mounting holes 46 (see FIG 1) by means ofwhich it can be mounted on any convenient support structure. Specialmounting brackets normally are not required because infinite angularadjustment of the arm 18 is provided by the worm gear 34 and rotatablehead 14. Adjustment of the position of arm 18 on shaft 16 can be made byloosening a screw 47 which draws the split lower ends of the arm 18together and causes the arm to grip the shaft.

A removable front cover plate 48 and a gasket 49 are secured to thefront of the housing 21 by means of a pair of screws 50. The gasket 49provides a water, oil and dirt-tight seal for the cover. A threaded hole52 is provided in the bottom of the housing for an electrical connectorto lead wires from the switch 30 to external electrical circuitry.

Referring now to FIG. 2, the cam head 14 includes a body portion 54, anda cover 56 and gasket 57 which are held in place on the body portion 54by means of screws (not shown). A horizontal hole is provided into whichthe shaft 16 is fitted. This hole is lined with bearings 58 and 60against which the shaft 16 rotates. The body portion 54 has a verticalcylindrical portion 62 which extends downwardly into the housing 12. Thecam follower rod 26 is mounted slidably in a central hole in thecylindrical portion 62. A snap-ring 64 fits into a groove near the endof portion 62, and abutts against the undersides of horizontal ledges 66(see FIG. 1) through which pass the mounting holes 46 and the holes forscrews 50. The body member 54 has a downwardly extending annular portion68 fitted into an annular recess in the top of the housing 12. Thejunction between portion 68 and housing 12 is sealed by means of asealing ring 70, thus providing an impervious seal. There is relativelytight frictional engagement at this point between the head 14 and theswitch housing 12. This tends to aid the worm 34 in holding the head inthe position to which it is adjusted.

Referring now to FIGS. 3 through 7, the cams 22 and 24 are mounted on aportion 72 of the shaft 16 which is of generally triangular crosssection, with the points of the triangle being rounded (see FIG. 5). Inaccordance with one advantageous feature of the present invention, theearns 22 and 24 are identical but are mounted on the shaft portion 72 inopposed relationship to one another. Each has an eccentrically locatedhole shaped to fit relatively tightly onto the shaft portion 72. Eachcam has a camming portion 74 and an idler portion 76 of smaller diameterthan the camming portion 74. The camming portion 74 depresses thefollower 26 when it contacts the follower, whereas when the dwellportion 76 contacts the follower 26, it does not depress the follower.

As indicated above, the cams 22 and 24 are placed on the shaft inopposed relationship. That is, the cam 22 is mounted with its camportion 74 facing outwardly from the drawing as shown in FIG. 4, whereasthe cam 24 is turned around and mounted with its cam portion facingrearwardly as shown in FIG. 4.

The shaft 16 is mounted so as to be movable longitudinally in the head14. It is thus movable to three different positions each of whichprovides a different mode of actuation of the switch 30 by the arm 18.Referring again to FIG. 2, when the shaft 16 is pushed inwardly in thedirection indicated by arrow 78, the right end of shaft 16 is positionednear the rearmost portion of the horizontal hole in head 14, and therounded, partially conical upper end 79 of cam follower 26 contacts onlycam 22. As a result, the switch 30 is actuated only when the arm 18 isrotated in a clockwise direction from its portion shown in FIG. 1. Thisis because only the engagement of camming portion 74 of cam 22 causesthe depression of the cam follower, and this happens only when the arm18 is rotated in a clockwise direction.

Conversely, when the shaft 16 is pulled outwardly to its outermostposition (not shown in the drawings) the cam follower tip 79 contactsonly the cam 24. Since the camming surface 74 of cam 24 depresses thefollower 26 only when the am 18 rotates in a counterclockwise direction,the switch 30 is operated only by the counterclockwise and not by theclockwise rotation of arm 18.

The shaft 16 may be moved longitudinally to a third position locatedbetween the innermost and outermost positions. This position is shown inFIG. 4. When the shaft 16 is in this position, the tip 79 of camfollower 26 engages the surfaces of both cams 22 and 24. Thus, thefollower 26 is depressed not only when the arm 18 is rotated clockwise,but also when it is rotated in the counterclockwise direction.

When a mode of actuation has been selected, it is desired to lock theshaft 16 in the position selected. This is accomplished by means of alocking member 80, which is shown in FIGS. 4 and 6 as well as FIG. 2.Three longitudinally spaced grooves 82, 84 and 86 are positioned alongthe right end of shaft 16. Locking member has a rectangularly shapedlower portion with an approximately centrally located hole 88 with anextended lower portion of smaller diameter. The right end of the shaft16 passes through the hole 88. Locking member 80 has a pointed upper endportion 90 with a pointed tip upon which is fitted a button 92,preferably of plastic and press-fitted onto the pointed end 90. Button92 moves upwardly and downwardly in a recess 94 in the cover 56 of thehead 14. An O-ring seal 96 is provided to keep the head 14 sealed. Aspring 98 is positioned between the bottom of the recess 94 and theundersurface of the button 92 so as to normally thrust the lockingmember 80 upwardly.

When it is desired to shift the shaft 16 inwardly or outwardly, thebutton 92 is depressed by the user. This causes the member 80 to movedownwardly out of one of the slots 82, 84 or 86. Then the shaft 16 ispushed or pulled inwardly to a new position, the button 92 is released,and the spring 98 pulls the locking member 80 upwardly into a differentone of the grooves 82, 84 or 86. The spring 98 holds the member in thegroove and thus locks it in the position selected.

It can be seen from the foregoing that it is quite easy to change theactuation mode of the switch 10. The operator need merely press thebutton 92, push or pull the shaft 16 to the desired position, andrelease the button. This is a decided advantage over prior devices inwhich the shifting is time-consuming and complicated. Moreover, itprovides for three modes of actuation; clockwise, counterclockwise and acombination of clockwise and counterclockwise actuation.

It is desired to provide a spring return for the arm 18 so that it willremain in a neutral position after being rotated. This spring returnfunction is provided by the arrangement shown in FIGS. 7 and 2. Aninverted U- shaped member 100 is fitted over a portion of the shaft 16which has a flattened upper surface 102. The member 100 slides upwardlyand downwardly in a vertical guide structure 104. The member 100 has apair of projections 106 over each of which is fitted a coil spring 108.The upper end of each coil spring 108 fits into a recess 110 in thelower surface of the cover 56.

When the shaft 16 is turned either clockwise or counterclockwise, oneedge of the flattened portion 102 lifts the member 100 upwardly andcompresses the springs 108. When the rotating force is removed from theactuating arm 18, the springs 108 thrust the member 100 downwardly andreturn the shaft 16 to its neutral position with the flattened portionflush against the corresponding flattened portion of the member 100.

One significant advantage of this spring return arrangement is theprovision of twin springs 108 instead of only a single spring. Limitswitches must have a very high degree of reliability; that is, theyoften must be able to withstand millions of operations withoutmalfunction. Each of the springs 108 is strong enough to alone returnthe arm 18 to its neutral position without the aid of the other spring.Thus, if one of the springs should break, the switch will continueoperating. This increases the reliability of the switch 10substantially.

Another advantageous feature of the prevent invention is that removal ofthe cam head 14 is quite simple. The head 14 may removed by removing thecover 48 and the lock ring 64, and lifting the head 14 from the switchhousing 12. Thus, if and when the head portion should become worn out, awhole new switching device need not be purchased, and the switch neednot be removed from its mounting. Instead, a new head may be used toreplace the old head. Also, different types of heads may be used asdesired, without changing the mounting of the housing 12.

It should be noted that the switching device 10 is unique in the furtherrespect that despite the fact that the head 14 can be adjusted toanyposition within a full circle, such adjustment does not in any wayaffect the mode of actuation selected for the switching mechanism. Therod 26 is located along the axis of rotation of the head 14, and has asymmetrical conical end 79 with a hemispherically shaped tip. Thus, therelationship between the cam follower and the cams 22 and 24 remains thesame throughout any rotation of head 14.

The switching device 10 provides many cost savings to its user. First,the user does not need to stock a large number of mounting brackets toprovide variable angular positioning of the arm 18. Instead, by a simpleadjustment easily performed by the use of a screw driver entirely fromthe outside of the switching device, he can position the arm to anyangular position he desires. This adjustment can be made withoutbreaching the sealed enclosure of the switching mechanism, thuspreventing foreign matter from reaching the internal switch componentsand substantially increasing the life of the device.

Because of the great versatility of switches made in accordance with thepresent invention, the user need not stock as many different types ofthem as he would prior switches. This provides another very significantcost saving to the user.

As explained above, the switching device 10 has three different modes ofactuation, each of which can be selected without theuse of any toolswhatsoever. Moreover, the cam housing 14 and the switch housing 12 neednot be opened to provide this adjustment, thus maintaining the enclosurefor the switch 30 and the components in the housing 14 in a sealedcondition. Moreover, the switch 10 is relatively inexpensive to produce.The novel use of two identical earns 22 and 24 instead of a complicatedsingle cam provides notable cost savings.

The above description of the invention is intended to be illustrativeand not limiting. Various changes or modifications in the embodimentsdescribed may occur to those skilled in the art and these can be madewithout departing from the spirit or scope of the invention as set forthin the claims.

I claim:

1. Apparatus for actuating a control element, said apparatus comprising,in combination, a support structure, a shaft, cam means on said shaft, acam follower for actuation of -said control element, means for mountingsaid shaft on said support structure so as to be rotatable and movablelongitudinally with respect to said support structure, said cam meanshaving at least two portions spaced longitudinally on said shaft, one ofsaid portions being shaped to move said cam follower upon the rotationof said shaft in one direction but not in the other, and the other ofsaid portions being shaped to move said cam follower upon the rotationof said shaft in said other direction, a housing around said shaft andcam means, and locking means for selectively locking said shaft in aplurality of different longitudinal positions, said locking meansextending through a wall of said housing so as to be accessible from theoutside of said housing.

2. Apparatus as in claim 1 in which each of said cam portions is aseparate cam, each cam having substantially the same shape as the othercam, with one cam being positioned on said shaft in an orientationopposite to that of the other cam.

3. Apparatus as in claim 1 in which said shaft has a A plurality oflongitudinally spaced-apart grooves, said grooves so as to bring saidcam follower into engagement with both of said cam portionssimultaneously.

4. Apparatus as in claim 1 including spring-biased means for returningsaid shaft to an initial position at which said follower is notdepressed, said means including a pair of parallel springs each capableof so returning said shaft.

5. Apparatus as in claim 1 including an arm secured to said shaft and aroller mounted on said arm.

6. Apparatus as in claim 1 in which said cam portions are locatedclosely adjacent one another on said shaft, and in which said camfollower has an end which rides against said cam means, said end havinga width which is less than the width of either of said cam portions,whereby longitudinal adjustment of said shaft selectively brings saidend to bear against either of said cam portions alone, or both portionssimultaneously.

7. Apparatus as in claim 6 in which said cam follower end is generallyconical in shape.

1. Apparatus for actuating a control element, said apparatus comprising,in combination, a support structure, a shaft, cam means on said shaft, acam follower for actuation of said control element, means for mountingsaid shaft on said support structure so as to be rotatable and movablelongitudinally with respect to said support structure, said cam meanshaving at least two portions spaced longitudinally on said shaft, one ofsaid portions being shaped to move said cam follower upon the rotationof said shaft in one direction but not in the other, and the other ofsaid portions being shaped to move said cam follower upon the rotationof said shaft in said other direction, a housing around said shaft andcam means, and locking means for selectively locking said shaft in aplurality of different longitudinal positions, said locking meansextending through a wall of said housing so as to be accessible from theoutside of said housing.
 2. Apparatus as in claim 1 in which each ofsaid cam portions is a separate cam, each cam having substantially thesame shape as the other cam, with one cam being positioned on said shaftin an orientation opposite to that of the other cam.
 3. Apparatus as inclaim 1 in which said shaft has a plurality of longitudinallyspaced-apart grooves, said locking means including a locking membershaped to fit into each of said grooves, spring means urging saidlocking member towards said grooves, and means operable for selectivelydisengaging said locking member from each of said grooves, two of saidgrooves each being located so as to bring only one or the other of saidcam portions into engagement with said cam follower, and a third groovelocated intermediate said two grooves so as to bring said cam followerinto engagement with both of said cam portions simultaneously. 4.Apparatus as in claim 1 including spring-biased means for returning saidshaft to an initial position at which said follower is not depressed,said means including a pair of parallel springs each capable of soreturning said shaft.
 5. Apparatus as in claim 1 including an armsecured to said shaft and a roller mounted on said arm.
 6. Apparatus asin claim 1 in which said cam portions are located closely adjacent oneanother on said shaft, and in which said cam follower has an end whichrides against said cam means, said end having a width which is less thanthe width of either of said cam portions, whereby longitudinaladjustment of said shaft selectively brings said end to bear againsteither of said cam portions alone, or both portions simultaneously. 7.Apparatus as in claim 6 in which said cam follower end is generallyconical in shape.